Getter structure for electron discharge devices



June 28, 1949. A. M. SKELLETT 2,474,335

v GETTER STRUCTURE FOR ELECTRON DISCHARGE DEVICES Filed May 15, 1947 TATE-1- ALBERT N 5424457? IN VEN TOR.

Patented June 28, 1949 arret s'muorv r Foe ELECTRON DISCHARGE. DEVICES Albert Skellet t, Madison, N. J., assignor to N tiqn Union R d o rat n ewark,

N- a ati n? of elawa e Application May 1 3, 1947, Serial No. 747,780 11 C ims 5 1+ -5) hi nv n o relates o. evacuat devices such aselectron tubes, electric lamps and the like, and more particularly, to method nd mea s fer effecting clean-up of residual gases in such de- :vices.

A principal object of th invention relates t a novel gettering arrangement for evacuated de-. vice enerally.

Another princip l .objeetis to prov de a improved arrangement for theselective flask-lingo; I l

(gettering material or cleanrup mat ri l su h s i commonly used in the processing and final clea up of electron tubes, e ectric lamps nd th i e- Another object is to provide a f eque cy-sense tive gettering arrangement for electron tubes,

lectric lamps and .the like.

A feature of the invention relat s to a novel support .for a gett r .orsaseou cle np agent, which support is ccns ructedas a reson nt wave ine eet enersa a tue dcireuit and i ar ans d to be elec ively ener i ed b a particu ar ire? 'qu ncy a which zthe line is mainly resonant or tuned.

Anethe ieaturere at sto,asup ert or a s t ma e wh ch ,sunpertis onstructed as a wave membe aedis arrange to hee ers zee b altern tins cur nt en rsra t e res.chalet i e- Iiiuens tor ocuee a ocaliz d urrent oncentra- -.t. 9. or maximizationf ther a rerelate t a setterine lem nt which enablestbe setterm ter a to be selec vel flashed and which enables the trajectory of the las edmate ial to be mor rsetlilr direct d A f he r f ature, re ates e an upport for s tterins material and the like A still -.fi. rth r s... or anizati n ar angement and e ative l a io aniprenert en n e -na ts wh ch o pera e to provide a more accurately controllable gettering proc dure forevacuateddevices, such as, electron discharge tubes, electriclamps and the like.

.Other .features andadvantages not specifically enumerated will appear as the ensuing description progresses.

In the drawing,

' r -[11 s a s allse 119 oi ra io are ln, 9 i e atins th nov s tt...,. .ns fla iaef mset .a seislies he; luv-e Fig. 2 is mentor Fig. 1,

. ameditati ns;tlies tsensslsmsst of Fig fir Linea .le eaHy tuned tare. re ate o the ovel av viiieg'nified ere? th setter ps ale Fig. 5 is a furthermodification of the gettering element of Fig. 1.

Referring to Fig. 1, there is shown in generalized iorm, a radio tube of any well-known construction, comprising an enclosing envelope II], which houses any well-known construction and assembly of electrodes represented, for example, by the electron-emitting cathode ll, control grid l2 and plate or anode .13. It will be understood thatthe showing of these electrodes is essentially schematic, and the inventive concept is not limited to any particular number or configuration of the electrodes. In the usual manner, the envelope iii carries an exhaust tubulation 14, by means of which the envelope l0 can be connected to a suitable vacuum pump. During the pumping schedule, it is usually necessary to raise the various metalparts within the envelope Hi to a sufilciently high temperature to drive out occluded gases and the like. When the pumping schedule has been completed, it is then necessary to subject the interior of the envelope to a final gas clean-up or gettering action. It has always been a problem in this art to enable the parts to be outgassed during the pumping schedule without, at-the same time, causing the usual gettering material to be heated sufficiently to vaporize it, since this gettering operaion is usually the final step before actual closing or sealing off the tubulation I4. This problem is particularly difiicult when the bombarding or outgassing of the metal parts and the subsequent flashing of the getter are effected by high frequency induction heating.

Various expedientshavebeen proposed heretofore to efiect thistirned or selective flashing of the getter with respect to the bombarding temperatures. The most common expedient has been to use a support'for the getter material, which support is so oriented with respect to the magnetic fiield of the induction heating coil that, during the normal outgassing or bombarding of the parts, the getter support is substantially unaffected by the high irequency induction field. It becomes necessary with the usual arrangement either to change the orientation of the field pro-.

tubes, particularly in some of the more recent miniature tubes, the parts are so small that reliance cannot always be placed upon the difference in location of the getter with relation to the other parts within the tube to effect the selective or timediliashing oi the getter material. The above-noted, and other disadvantages, are

overcome according to the present invention, by constructing the getter support in such a Way that it is highly frequency-sensitive. For this purpose, the getter support is constructed as a wave resonant element which may take any suitable form in the nature of a resonant wave transmission line section or tuned circuit organization. Thus, as shown in Figs. 1 and 2, the getter support is in the form of a relatively small metal ring [5, which is attached by a thin metal arm Hi to any suitable part of the electrode assembly within the tube. The region ll of this ring is reduced in thickness and carries the gettering material 53 which may be of any well-known chemical composition. While the drawing shows the ring with its plane parallel to the vertical axis of envelope [0, it will be understood that the ring 85 may be located in any other convenient plane. When it is desired to outgas the metal parts within the envelope Hi, the usual bombarding coil H3 may be lowered over the tube and the coil 19 may be excited with any suitable high frequency current sufficient to raise the parts to their outgassing temperature. However, because of the small dimensions and relative thinness of the ring [5, insufiicient heating may be generated in this ring I5 by the coil l9 to raise the material I8 to the vaporizing temperature.

After the parts have been outgassed, the coil l9 may be energized by a different high-frequency current whose frequency however is correlated with the resonant characteristics of the ring l5 considered as a wave transmission line, or tuned circuit organization. If desired, instead of using the same coil [9 for this purpose, a separate coil 20 may be employed and connected to a suitable source of ultra high-frequency energy. It is a well-known phenomenon in high-frequency wave transmission lines that by suitable proportioning of the line, with respect to the excitation frequency. that current nodes and current maxima can be produced at particular points along the line. Advantage is taken of this fact to locate the thinned-out portion ll of ring [5 at such a that a current maxima appears in the ring I5 at this region when the ring I5 is excited by a suitable high-frequency electromagnetic wave energy as above described. In determining the frequency for this wave energy, the following formula can be followed:

wherein (1 equals the radius of ring l5, and r equals the radius of the wire of which ring [5 is fabricated.

Instead of making the getter support in the form of a complete ring, it may be constituted of composite inductive and capacitive elements. Thus, as shown in Figs. 3 and 4, the getter support consists of a discontinuous metal ring 2|, similar to ring I 5, but having a small gap 22 between the ends thereof, each gap end carrying a small metal disc or plate 23, 24, to form therebetween a capacitor of predetermined capacitance. This capacitance, in conjunction with the inductive reactance of the ring 2|, forms a tuned circuit which resonates at the frequency of the electromagnetic wave energy supplied by field coil 20. Here again, the ring 2| has a thinned portion to which is applied the getter material 26.

physical parameters of the point Fig. 5 shows a further modification wherein the getter support is in the form of a one-quarter wavelength transmission line or Lecher wire comprising a pair of parallel metal wires 21, 28, which are approximately equal in length to onequarter of the wavelength of the alternating current energy supplied by coil 20. The wires 21 and 28 are short-circuited by the portion 29 which is thinned out at the region 30, and at this region there is applied the getter material 3|.

In all the foregoing embodiments, the flashing of the getter material will be selectively responsive to the resonant frequency for which the respective supports are designed, and the flashing heat will be mainly localized at the thinned-out portions IT, 25 and 29, both by reason of the higher ohmic resistance at this thinned-out portion and by reason of the fact that in accordance with one transmission line theory a current maxima. will occur at this thinned-out region. Furthermore, since the flashing heat is thus 10- calized, there is provided more control over the trajectory of the flashed material as it is being vaporized, so that it can be more readily directed, for example by appropriate positioning of the getter support, towards a desired area of the envelope I0.

While certain embodiments have been disclosed herein, various changes and modifications may be made therein without departing from the spirit and scope of the invention. Thus, instead of making the resonant member of a wire carrying a coating of getter material, the Wire itself may be constituted of conductive getter material.

What is claimed is:

l. A gettering unit to be heated by high frequency wave energy, comprising a support, getter material on said support, said support being constituted of a conductive member which in itself forms a tuned electrical circuit selectively resonant at the frequency of said wave energy to convert said wave energy into heat energy for flashing the getter material.

2. A gettering unit to be heated by high frequency wave energy, comprising a support, getter material on said support, said support being constituted of a conductive member which is physically shaped to form in itself an electrical wave transmission line resonant at the frequency of said wave energy to convert said wave energy into heat energy for flashing the getter material.

3. A getter support to be heated by high-frequency Wave energy, said support comprising a tuned conductive ring whose dimensions are proportioned to cause it to resonate electrically as a wave transmission line at said high frequency, said ring having a thinned-out portion supporting getter material.

4. A getter support according to claim 3 in which said thinned-out portion is located at a region of maximum current resulting from the resonating of said ring at said high frequency.

5. A getter support to be heated by high-frequency energy, said support comprising a discontinuous metal ring having a predetermined inductive reactance and with a gap between the ends, and capacitor members attached to said ends tuning said inductive reactance to resonate at said high frequency.

6. A getter support for selective heating by a particular high frequency wave, said support being in the form of a tuned conductive member forming a wave transmission line section which selectively resonates to Produce at least one region of current maximum when excited by said high frequency, and a quantity of getter material applied to said member at said region.

7. A getter support according to claim 6 in which said region of said conductive member is thinned out with respect to the remainder of said member.

8. A getter support for heating by a particular high frequency, said support being in the form of a Lecher-Wire Wave transmission line whose resonant frequency is correlated with the said high frequency to produce at least one current maximum at a predetermined region of the support, and a quantity of getter material applied to said support at said region.

9. A getter support in the form of a wire ring to be heated to getter flashing temperature by a high-frequency current to which said ring is selectively responsive, said frequency being substantially equal to where a is the radius of the ring and r is the radius of the wire from which the ring is formed, said ring having a thinned-out portion over a localized region supporting getter material.

10. A getter support according to claim 9 in which said localized region is located at a current maxima resulting from the electrical resonance of said ring at said high frequency.

ALBERT M. SKELLE'IT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,638,551 Ronci Aug. 9, 1927 1,997,053 Gill Apr. 9, 1935 2,090,981 Lederer Aug. 24, 1937 2,112,082 Espe Mar. 22, 1938 2,260,927 Atlee Oct. 28, 1941 2,445,447 Martin, Jr July 20, 1948 

